12.01.2013 Views

Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

CHAPTER I<br />

INTRODUCTION<br />

Transportation planners and analysts are often faced with the<br />

problem of estimating the demand <strong>for</strong> a particular mode of transpor-<br />

tation. Prospective transportation investments may take many <strong>for</strong>ms.<br />

Small or large alterations in the characteristics of an operating mode<br />

may be under consideration. The introduction of an alternative, but<br />

proven mode into the present system may be contemplated. Or, a com-<br />

pletely new and novel mode may have been proposed. In all of these<br />

cases the planners must be concerned with the effects of the structural<br />

change upon (1) the operation of the mode in question, (2) the opera-<br />

tions of all other modes in the system, and (3) the producers and con-<br />

sumers of the products which are transported.<br />

Implicit in the above questions are the assumptions that there is<br />

some overall demand <strong>for</strong> tranaportation and that the various modes com-<br />

pets <strong>for</strong> shares of the total traffic, i.e., that the modes are to some<br />

extent substitutes <strong>for</strong> one another. At the same time it is recognized<br />

that the modes may differ significantly in the service which they offer<br />

to the shipper. Somehow we believe these differences can be compared<br />

and we can speak of better services and, indeed, of better modes. In<br />

fact, we may even seek to determine which mode, or conceivable future<br />

mode, might constitute the optimum supply <strong>for</strong> certain transport needs.<br />

1

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!